Electrodeposition of a nickel-manganese alloy



United States Patent M 3,244,603 ELECTRODEPOSITION 01* A NICKEL- MANGANESE ALLOY William B. Stephenson, IL, Cincinnati, and Edward Farmer, Reading, Ohio, assignors to General Electric Company, a corporation of New York No Drawing. Filed June 8, 1962, Ser. No. 200,953 6 Claims. (Cl. 204-43) This invention relates to a nickel base, nickel-manganese alloy and, more particularly, to an electrodeposited nickel-manganese alloy suitable for use in a method of electroforming articles.

Electroforming, which is sometimes referred to as electrotabricating, is a process which has been used to cre ate articles of a variety of sizes and shapes. Examples of such articles are hypodermic needles, microscopic grooves of high fidelity record stampers, huge dish like molds for forming plastic canopies, fountain pen caps and electrotype. When accurately controlled, the electroforming process allows for the formation of intricate parts with accurate dimensions and at relatively low cost. However, one of the problems which must be solved before such a process can be adapted to the manufacture of articles to operate under highly stressed conditions such as in jet engines, is that the metal or metal alloy which is electrodeposited to form the desired article must have sufficient strength and ductility to withstand the diflicult conditions to which an article would be subjected in operation.

The present invention, in one form, has recognized that a particular aqueous electroplating bath can be used to develop a nickel base, nickel-manganese alloy of unusual strength characteristics.

Electroplating, of course, is a very old art and the plating of nickel and manganese in the same bath was reported in US. Patent 1,026,628-Leuchter in 1912. US. Patent 2,377,321-Brown et al., and 11.8. Patent 2,905,- 601, mention the formation of a nickel-manganese alloy in the electrodeposition art.

Although an electrodepo'sited alloy of nickel and manganese has been produced there still exist a number of difiiculties in producing such an electrodeposit in a crackfree condition and sufiieiently thick when formed as a structural member. However, it has been recognized that the co-electrodeposition of nickel and manganese under certain conditions can result in an unusual crack-free material which can have strength and ductility.

It is a principal object of this invention to provide an electrodeposited nickel-manganese alloy having unusual strength and ductility characteristics.

Another object is to provide an electrolyte and a method for electrodepositing a nickel-manganese alloy into an article shape which has strength characteristics unusual for an electroformed article.

These and other objects and advantages will become more apparent from the following more detailed discus sion and examples which are exemplary of rather than limitations on the scope of the present invention.

Briefly, the present invention provides an electroformed Mi-Mn alloy including less than 1 Weight percent manganese and preferably consisting essentially of 0.030.8 weight percent manganese with the balance nickel. Strong articles of the alloy of this invention can be electroformed from an aqueous sulfamate nickel electroplating bath in which the manganese metal content is about 25 ounces per gallon and the nickel metal content is about 10l2 ounces per gallon, with the bath being operated at a temperature above about 120 F. preferably at a current density or" between about 20-75 amps per square foot.

Although a variety of nickel electroplating baths or electrolytes are well known in the art of electroplating,

Patented Apr. 5, 1966 it Was recognized that sulfamate type baths produce electrodeposits better suited for high temperature applications. This was demonstrated by testing a number of different nickel plating solutions two of which are represented as follows:

Aqueous solution A Nickel metal oz./gal 1 10.010.5 Boric acid do 4.5-5.0 pH 4.0-4.2 Temperature F 140 Current density amps/sq. ft 50 1 As nickel sulfamate.

Aqueous solution B Nickel sulphate oz./gal 24 Ammonium chloride do 3.5 Boric acid do 4.0 pH 3.5 Temperature F Current density amps/sq. it 50 The following" Table I presents average ultimate tensile strength (-UTS) data in thousands of pounds per square inch at three different temperatures with the electrodeposited material of about 0.030" thick having been pre-treated under several different conditions.

TABLE I Temp. Anneal Avg. Elongation Solution F.) Temp. U'IS (percent) F.) (k.p.s.i.)

Room As plated 141 11 Room As plated 112 5 Room 750 117 15- Room 750 75 25 750 750 69 12 750 750 36 11 750 1,100 39 31 750 1,100 3 5 1,100 1,100 18 6 1,100 1,100 7 18 It is readily recognized that up to a temperature of about 1100 F., the sulfamate type of bath represented by Aqueous Solution A has better characteristics for high temperature operation.

It was recognized from the following. Aqueous Solution C that the addition of manganese as an alloying element with nickel resulted in unusual properties.

The electrolyte solution used was as follows:

Aqueous solution C Oz./ gal. Nickel metal (as sulfamate) 1.0.5 Manganese metal (as sulfamate) 4.0 Boric acid 4.0

Aqueous Solution C at a pH of 3.5 and a temperature of F. was used at a current density of about 60 amps/sq. ft. with depolarized nickel anodes to produce a nickel-manganese alloy sheet 8" X 10" x 0.030". This material of 0.4 weight percent Mn, balance Ni showed that the hardness and heat stability of nickel alone is changed markedly by the inclusionof manganese.

As a result of this initial discovery, a number of sample solutions were tested. Some of these are presented in Table II along with the conditions under which sheets of 0.030 inch thick alloy was produced. Table III gives the Weight percent of manganese in each sheet, the balance of which was nickel. Comments as well as hardness figures regarding the physical conditionof the electrodeposited alloy are included.

TAB LE II.-ELE C T ROLYIE BATH Ni Mn Temp. Current Example (oz./gal,) (oz./gal.) pH F.) density (amps. lit!) TAB LE IIL-PLATED DEPOSIT Example Mn (Wt. Stress 1 Hardness, Physical percent) R a con ditlon 1. 2 D. 1. 2 D. 0. S O 0. 6 A. 0. 5 A. 0. 3 A.

4. 5 D. 0. 9 D. 0. 6 A. 0. 2 A. 0. 03 A.

0. 6 B. 0. 4 A. 0. 5 A. E.

1 I-I=l1igh. M=rnoderate. S=slight. VS=very slight. A=S0und. B=Slightly brittle. G=fine cracks along edges. D= cracked and brittle. E =1nany gas pits, soft and granular.

It is to be noted that with less than 1 weight percent manganese, the hardness and heat stability of the nickelmanganese alloy is markedly changed. Generally, the manganese content decreases as the temperature of the electroplating bath increases while the manganese content increases with current density. However, the manganese content was generally unaffected by variations in pH between about 1 and 5, although the physical condition of the alloy deposited at a pH of 1 was unusually poor as compared with that produced at a pH of 2. Examples 1-6 represent variations in the manganese content of the bath; Examples 7, 8, 18 and 19 represent variations in the current density at two different temperatures; Examples 9-13 represent variations in bath temperature and Examples 14-17 represent the efiect of change in pH.

The hardness data shows that an alloy hardness of above about 40 Rockwell C (R results in too high a stress level in the alloy and leads to cracks in the material. Furthermore, a manganese content below about 0.8 Weight percent of the alloy results in a sound, strong alloy whereas alloys containing manganese at or above about 1.2 weight percent are brittle and highly stressed.

From aqueous solution C and those in Table II, it has been found that the manganese metal content in the electrolyte of this invention lies in the range of about 2-5 ounces per gallon and the nickel metal content lies in the range of about -12 ounces per gallon. Both of the metals are present in the aqueous bath as metal sulfamate along with an agent such as boric acid normally used in nickel electroplating solutions. Furthermore, the temperature should be maintained above F., generally within the range of 120-160 F. and preferably in the range of -150" F. The pH between 2-5 resulted in satisfactory alloy with extraordinary material being produced at a pH between about 2-4. Excellent material was deposited at current densities between 20-75 amps per square foot but the electrodepositon of the nickel-manganese alloys from an aqueous bath at a temperature of 120 F. or less resulted in a highly stressed material which was cracked and brittle.

The data shows that an electroformed Ni-Mn alloy deposited from a sulfamate solution and including less than 1 weight percent Mn and preferably consisting escentially of 0.03-0.8 weight percent manganese with the balance nickel has unusual characteristics which were unrecognized prior to the present invention.

In order to evaluate the strength properties of the alloy of the present invention, a series of 8" x 10" rectangles 0.03 thick were prepared from the following sulfamate plating bath and under the listed conditions to result in a composition of 0.5 Weight percent manganese with the balance nickel.

Nickel metal content (as sulfamate) oz/gal. 10.5-11.0 Manganese metal content (as sulfamate) oz./gal. pH Temperature F. Current density amps/sq. ft. Hardness R Prior to testing, the alloy rectangles were stabilized by heating at 800 F. for 16 hours and then air cooling to insure that no changes in the material would take place as a result of exposure to the test temperatures and to remove any entrapped hydrogen which is known to exist in slight amounts in the as-plated condition.

It has been found that any brittleness which might exist in the as-plated condition within the range of the alloy of this invention, is caused mainly by cathodic hydrogen content. be imparted to such alloy by a low temperature anneal to degas the material without loss in strength.

The specimens made from the alloy rectangles were 0.350" wide by 2" gage length. The following Table IV gives the average tensile properties of such specimens.

TABLE IV.TENSILE PROPERTIES Temp. F.) Avg. UTS Avg. elonga- Avg. hard- (k.p.s.i.) tion (percent) ness (Re) It is to be noted that the Ni-Mn alloy of the present invention is substantially stronger than the Ni-metal specimens, the data for which is shown in Table I.

A photomicrograph of a cross section of the electrodeposited NiMn alloy of this invention have shown that the alloy does not have the conventional crystal structure that would normally be attributed to this type of alloy. The appearance of the structure is similar to that of untempered martensite. It is believed that the fine as-plated grain size is primarily responsible for the high mechanical properties of this alloy.

Although this invention has been described in connection with specific examples, it will be readily recognized by those skilled in the art of electrodeposition, the variations and modifications possible within the scope of the invention described.

In such a case, adeqaute ductility can What is claimed is:

1. An alloy of nickel and manganese electrodeposited from a sulfamate electrolyte and consisting essentially of 0.03-0.13 weight percent manganese with the balance nickel, the alloy having a hardness of less than about 40 Rockwell C.

2. An alloy of nickel and manganese electrodeposited from a sulfamate electrolyte and consisting essentially of 003-08 weight percent manganese, with the balance nickel, the alloy having a hardness between 20-40 Rockwell C.

3. For electrodepositing an Ni-Mn alloy of up to about 1 weight percent manganese, an aqueous electrolyte consisting essentially of:

a manganese metal content of 2-5 oz./gal., and

a nickel metal content of -12 oz./gal.;

the manganese metal and the nickel metal being in the electrolyte in the form of sulfatnates; and

the electrolyte having a pH of about 2-5.

4. For electroclepositing an Ni-Mn alloy of up to about 1 weight percent manganese, an aqueous electrolyte consisting essentially of:

a manganese metal content of 3.5-4 oz./gal.; and

a nickel metal content of 105-11 oz./gal.;

the manganese metal and the nickel metal being in the electrolyte in the form of sulfamates; and

the electrolyte having a pH of about 3.5-4.

5. In a method for electrodepositing an Ni-Mn alloy, the steps of:

electrolyzing an aqueous electrolyte consisting essentially of a manganese metal content of about 2-5 oz./ gal. and a nickel metal content of about 10-12 oZ./ga1., the manganese metal and the nickel metal being in the electrolyte in the form of sulfamates; and

during electrolyzing, maintaining the electrolyte pH at about 2-5 and the temperature above about 120 F.

6. In a method for eiectrodepositing an Ni-Mn alloy, the steps of:

electrolyzing at a current density of about 20-75 amps/ sq. ft. an aqueous electrolyte consisting essentially of a manganese metal content of 2-5 oz./ gal. and a nickel metal content of 10-12 oz./gal., the manganese metal and the nickel metal being in the electrolyte in the form of sulfamates; and

during electrolyzing, maintaining the electrolyte pH at 2-5 and the temperature between and F.

References Cited by the Examiner UNITED STATES PATENTS OTHER REFERENCES Metal Finishing Guidebook Directory, 29th edition, page 344, 1961.

P-iontelli et al., Proc. of the Third Intl. Conference on Electrodeposition, Electrodepositors Technical Society, September 1947, pp. 121-125.

JOHN H. MACK, Primary Examiner.

JOHN R. SPECK, Examiner.

G. KAPLAN, Assistant Examiner. 

1. AN ALLOY OF NICKEL AND MANGANESE ELECTRODEPOSITED FROM A SULFAMATE ELECTROLYTE AND CONSISTING ESSENTIALLY OF 0.03-0.8 WEIGHT PERCENT MANGANESE WITH THE BALANCE NICKEL, THE ALLOY HAVING A HARDNESS OF LESS THAN ABOUT 40 ROCKWELL C.
 3. FOR ELECTRODEPOSITING AN NI-MN ALLOY OF UP TO ABOUT 1 WEIGHT PERCENT MANGANESE, AN AQUEOUS ELECTROLYTE CONSISTING ESSENTIALLY OF: A MANGANESE METAL CONTENT OF 2-5 OZ./GAL., AND A NICKEL METAL CONTENT OF 10-12 OZ./GAL.; THE MANGANESE METAL AND THE NICKEL METAL BEING IN THE ELECTROLYTE IN THE FORM OF SULFAMATES; AND THE ELECTROLYTE HAVING A PH OF ABOUT 2-5. 